Carla Gaiolas

Green chemicals and process to graft cellulose fibers

The treatment of additive-free hand sheet paper samples with cold plasma was carried out and showed that cellulose can be chemically linked with reactive natural products, namely myrcene (My) and limonene (LM). Contact-angle measurement and X-ray photoelectron spectroscopy (XPS) were used to ascertain the occurrence of the grafting. Indeed, the contact-angle value of a drop of water deposited at the surface of paper increased from 30 degrees for unmodified substrate to about 105 and 107 degrees, for LM- and My-treated samples, respectively. In fact, LM- and My-treated surfaces were rendered totally apolar. Indeed, the polar contribution to the surface energy decreased from about 23 mJ/m(2) for pristine samples to practically zero for treated ones. The treated surfaces displayed water-barrier properties; the penetration of the liquid was reduced significantly after LM and My treatments. The XPS spectra showed that the modification with LM and My gave rise to very significant change in the O/C ratio, as well as in the intensity of the C1 peak assigned to aliphatic carbon sequences.

Cold-plasma assisted grafting of cellulose fibres by acrylic monomers

Additive-free hand sheet paper samples were activated by cold-plasma in the presence of acrylic acid (AAc), acrylamide (AAm), methyl acrylate (MAc) and methyl methacrylate (MMa). The characterisation of the modified substrates showed that there grafting has occurred efficiently, as established by weight gain and FTIR spectroscopy. The contact angle measurement were carried out, as a function of pH and showed that the deposition of a drop of water at the surface of the tested samples formed 55° for unmodified substrate to 87°, for MMa-treated papers, respectively, indicating that the surface has became totally hydrophobic. ATR-FTIR spectroscopy was used to check the grafting efficiency.

Cold-plasma assisted hydrophobisation of cellulose fibres with styrene and para-halogenated homologues

Cold-plasma-assisted treatment of additive-free hand sheet paper samples with styrene (ST), para-fluorostyrene (FST), para-fluoro-α-methylstyrene (FMST) and para-chloro-α-methylstyrene (ClMST) and para-bromostyrene (BrST) was studied and found that the grafting has occurred efficiently, as established by contact angle measurement. Thus, after solvent extraction of the modified substrates, in order to remove unbounded grafts, the contact angle value of a drop of water deposited at the surface of paper increased from 40° for unmodified substrate to 102, 99, 116, 100 and 107°, for ST-, FST- FMST-, ClMST- and BrST-treated samples, respectively, indicating that the surface has became totally hydrophobic. In fact, the polar component of the surface energy of treated samples decreased from 25 mJ/m2 to practically zero, indicating that treated surfaces were rendered totally non polar.